1. Field of the Invention
This invention relates to a method and device for replacing upper and lower dies in a bending processing machine, such as, for example, a press brake. More specifically, it relates to a exchange method and device in which a long die in the bending processing machine is separated into a number of parts.
2. Description of the Prior Art
Previously, dies used in a bending processing machine such as a press brake have been replaced by simply transporting them in and out by means of a die exchange device on one side of the bending processing machine. Consequently, the die exchange device must have sufficient width to hold a very long die and takes up as much space as the bending processing machine, itself. That is to say, previously die exchange devices have been large and occupied a large area.
In addition, in general a rack device is used as the exchange device which holds and supports metal dies in a bending processing machine. However, to automate the exchange of dies in a bending processing machine, a device has been developed in which a number of link members are pivotally linked in an endless configuration and several link members form a die holder which holds the die. In such a configuration, it is necessary for the link members to be guided by a rigid guide rail to avoid problems when supporting a heavy die.
Existing die exchange devices having the configuration described above have separate sets of link members to hold upper dies and lower dies. This means that separate metal die insertion and removal transport devices are needed for the upper dies and lower dies. Consequently, existing die exchange devices have a number of problems such as that their construction is complicated and transport is difficult.
In addition, since the dies used in bending processing machines are long and very heavy, when the dies are supported by link members that are pivotally linked in a loop, there are problems such as that looseness occurs.
In an existing device in which the metal holders which hold the die are linked in a loop, the die holders are formed on the outsides of linked members which are linked in a loop. Consequently, the center of gravity is toward the outside, so that when the link members which are linked in a loop with dies in the die holders and when they move from the straight line to the circular arc section of the guide rail, speed increases and inertia becomes large, so that excessive load is placed on the motor and indexing of the dies becomes difficult.